1. Field of the Invention
This invention is directed to protectors, stabilizers, and centralizers for use in wellbore operations, including, in one specific embodiment centralizers for use with casing. In another embodiment this invention is particularly directed to devices which create or enhance turbulence in well fluids with a nozzle effect.
2. Description of Related Art
In various well operations a tubular member used in a wellbore needs to be protected, stabilized, or centralized. For example, wellbores are often lined with a string of casing. The casing is held in place by cement which, prior to hardening, is pumped down the string of casing and then flows out from the bottom of the casing and thence upwardly in the annulus between the exterior of the casing and the interior of the wellbore. A variety of problems are encountered if the casing is not centered in the wellbore. It is also important for the upflowing cement to push ahead of it any drilling mud that may have remained in or on the wellbore. Various devices and methods have been employed to provide for centralizing the casing and to tubulently "scour" unwanted mud cake from the interior wall of a wellbore.
Stabilizers for drill pipe are common. They are employed to inhibit or prevent transverse movement of drill pipe within a well while permitting normal free rotation and longitudinal movement of the pipe. Various stabilizers have protruding ribs which define longitudinal passages which permit circulation of drilling fluids and of cuttings resulting from drilling. Drill pipe stabilization controls deviation of a wellbore, minimizes the severity of doglegs, and optimizes drill pipe performance by providing for coaxial rotation. Stabilizers are available as sleeves or as an integral string component.
In accordance with 37 C.F.R. 1.56 the following are disclosed:
U.S. Pat. No. 3,072,195 discloses a slip over collar-type centralizer which attempts to create a turbulent action in a cement slurry so that the swirling action of the cement will remove mud cake clinging to the wellbore walls. This is accomplished by an agitator device which has a plurality of inclined blades.
U.S. Pat. No. 2,973,996 discloses a stabilizer for drill pipe with a plurality of spiral-shaped ribs.
U.S. Pat. No. 4,658,896 discloses a centralizer with a plurality of protuberances for imparting turbulent action to a cement slurry and structure to clean mud cake from a wellbore wall.
U.K. Patent No. 2,171,436 discloses a centralizer/stabilizer with a plurality of extending rigid blades.
"Oilfield Products and Equipment," page 1, Weatherford 1988 Annual Report shows a general diagram of a typical drilling operation.
"Products and Services Catalog 1986-87," Weatherford 1985, discloses typical centralizers, wipers, and clamps, pages 22-30; and typical stabilizer sleeves, page 43.
Related prior art of which applicants are aware include
U.S. Pat. Nos. 1,460,632; 1,767,198; 2,237,863; 2,312,600; 2,388,416; 2,424,027; 2,622,684; 2,636,564; 3,164,216; 3,397,017; 4,042,023; 4,422,504; 4,766,663 (Division of U.S Pat. No. 4,658,896); Canadian Patent No. 1,231,642; U.K. Patent No. 2,138,056B and "Christensen Downhole Tools--Stabilizers" pages 2034-2041.
There has long been a need for a downhole device that creates or enhances turbulence in a flow of material in a wellbore such as, but not limited to, drilling fluid, drilling fluid with cuttings or other material, or cement slurries.